perl - Perl 的隐藏功能？

Question

锁定。这个问题及其答案是locked因为这个问题是题外话，但具有历史意义。它目前不接受新的答案或互动。








Perl 中有哪些真正有用但深奥的语言特性，您实际上能够用来做有用的工作？

准则:

尝试将答案限制在 Perl 核心而不是 CPAN

请给出示例和简短说明

在其他语言的隐藏功能中也发现了隐藏功能:

(这些都来自 Corion's answer)

C

达夫的装置

便携性和标准性

C#

空格分隔列表和字符串的引号

可别名命名空间

Java

静态初始化器

JavaScript

函数是一等公民

块作用域和闭包

通过变量间接调用方法和访问器

Ruby

通过代码定义方法

PHP

无处不在的在线文档

魔术方法

符号引用

Python

一行值交换

甚至可以用您自己的功能替换核心功能

其他隐藏功能:

运营商:

The bool quasi-operator

The flip-flop operator

也用于 list construction

The ++ and unary - operators work on strings

The repetition operator

The spaceship operator

The || operator (and // operator) to select from a set of choices

The diamond operator

Special cases of the m// operator

The tilde-tilde "operator"

引用结构:

The qw operator

Letters can be used as quote delimiters in q{}-like constructs

Quoting mechanisms

语法和名称:

There can be a space after a sigil

You can give subs numeric names with symbolic references

Legal trailing commas

Grouped Integer Literals

hash slices

Populating keys of a hash from an array

模块、编译指示和命令行选项:

use strict and use warnings

Taint checking

Esoteric use of -n and -p

CPAN

overload::constant

IO::Handle module

Safe compartments

Attributes

变量:

Autovivification

The $[ variable

tie

Dynamic Scoping

Variable swapping with a single statement

循环和流量控制:

Magic goto

for on a single variable

continue clause

Desperation mode

正则表达式:

The \G anchor

(?{}) and '(??{})` in regexes

其他特点:

The debugger

Special code blocks such as BEGIN, CHECK, and END

The DATA block

New Block Operations

Source Filters

Signal Hooks

map ( twice )

Wrapping built-in functions

The eof function

The dbmopen function

Turning warnings into errors

其他技巧和元答案:

cat files, decompressing gzips if needed

Perl Tips

另请参阅:

Hidden features of C

Hidden features of C#

Hidden features of C++

Hidden features of Java

Hidden features of JavaScript

Hidden features of Ruby

Hidden features of PHP

Hidden features of Python

Hidden features of Clojure

Answer 1

触发器运算符可用于在循环遍历文件句柄返回的记录(通常是行)时跳过第一次迭代，而不使用标志变量:

while(<$fh>)
{
  next if 1..1; # skip first record
  ...
}

运行 perldoc perlop并搜索“触发器”以获取更多信息和示例。